Question

What results when a secondary alcohol is oxidized? a. a ketone d. an acid b. an amine e. no reaction c. an aldehyde Which of the following combinations will react spontaneously? A. 12 + Cu2+ B. Pb2+ + Ag C. Zn2+ + Mg D. Sn2+ + Ni2+ The general formula for a cycloalkane can be represented by which of the following? a. C,H, C. CH b. C.H2n+2 d. C.H21-2 In a certain reaction AH =-136 kJ and E, = 96 kJ. Which of the following is true of its reverse reaction? A. The reverse reaction is exothermic and E, = -40kJ. B. The reverse reaction is exothermic and E, = 40kJ. C. The reverse reaction is endothermic and E, = 96 kJ. D. The reverse reaction is endothermic and E. = 232 kJ. Consider the following reaction mechanism: Step 1 0, 0, +0 0, +020, Step 2 Which of the following could represent the activated complex for Step 2? A. O B. O2 CO D. O

Answer 1

As per rules the first four will be answered.

1. A secondary alcohol gets oxidised to a ketone.

он KMnO4 [O]

Correct option is A.

2. Zn²⁺ react with Mg spontaneously as follows:

Zn²⁺ + Mg $\rightarrow$ Mg²⁺ + Zn

I₂ + Cu²⁺ $\rightarrow$ No reaction. (For a redox reaction to happen, one species need to get oxidised and the other needs to get reduced. But here reduction happens for both I₂ and Cu²⁺ which is not possible).

Ag + Pb²⁺ $\rightarrow$ No reaction. (Since Ag is less reactive than Pb, Ag cannot displace Pb from its salt solution).

Sn²⁺ + Ni²⁺ $\rightarrow$ No reaction. (For a spontaneous process the E^o_cell should be positive. But here the E^o_cell = -0.08 V i.e negative. So it is non-spontaneous).

Correct option is C.

3. Some cycloalkanes are C₃H₆, C₄H₈, C₅H₁₀. As you can see the general formula would be C_nH_2n where n = number of carbon atoms.

Correct option is C.

4. Given, E_a(forward) = 96 kJ

$\Delta$H = -136 kJ

Note: $\Delta$ H = E_a(forward) - E_a(reverse)

Putting the values we get,

-136 kJ = 96 kJ - E_a(reverse)

E_a(reverse) = 96 + 136 = 232 kJ

Since the forward reaction is exothermic as $\Delta$ H = negative, the reverse reaction must be endothermic.

Correct option is D.